/*
 * 
 */

package com.generalynx.common.filters;

import java.io.IOException;
import javax.servlet.*;

public class SetCharacterEncodingFilter implements Filter {
    /**  The default character encoding to set for requests that pass through this filter. */
    protected String encoding = null;

    /** The filter configuration object we are associated with.  If this value is null, this filter
     *  instance is not currently configured. */
    protected FilterConfig filterConfig = null;

    /** Should a character encoding specified by the client be ignored? */
    protected boolean ignore = true;

    /** Take this filter out of service. */
    public void destroy() {
        this.encoding = null;
        this.filterConfig = null;
    }

    /**
     * Select and set (if specified) the character encoding to be used to interpret request
     * parameters for this request.
     *
     * @param request  The servlet request we are processing
     * @param response The servlet response we are creating
     * @param chain    The filter chain we are processing
     * @throws IOException      if an input/output error occurs
     * @throws ServletException if a servlet error occurs
     */
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            throws IOException, ServletException {
        // Conditionally select and set the character encoding to be used
        if (ignore || (request.getCharacterEncoding() == null)) {
            String encoding = selectEncoding(request);
            if (encoding != null) {
                request.setCharacterEncoding(encoding);
            }
        }
        // Pass control on to the next filter
        chain.doFilter(request, response);
    }

    /**
     * Place this filter into service.
     *
     * @param filterConfig The filter configuration object
     */
    public void init(FilterConfig filterConfig) throws ServletException {
        this.filterConfig = filterConfig;
        this.encoding = filterConfig.getInitParameter("encoding");
        String value = filterConfig.getInitParameter("ignore");
        if (value == null) {
            this.ignore = true;
        } else if ("true".equalsIgnoreCase(value)) {
            this.ignore = true;
        } else {
            this.ignore = "yes".equalsIgnoreCase(value);
        }
    }

    /**
     * Select an appropriate character encoding to be used, based on the characteristics of the
     * current request and/or filter initialization parameters.  If no character encoding should be
     * set, return <code>null</code>. <p> The default implementation unconditionally returns the
     * value configured by the <strong>encoding</strong> initialization m_parameter for this
     * filter.
     *
     * @param request The servlet request we are processing
     */
    protected String selectEncoding(ServletRequest request) {
        return (this.encoding);
    }
}
